1. Field of the Invention.
This invention concerns prosthetic dentures of the type wherein either the maxillary or mandibular natural dentition is to be replaced by the prostheses.
2. Description of the Prior Art.
A major concern in the design and manufacture of such prosthetic dentures is the fit of the dentures to the edentulous area of the patient's mouth and also the position of the teeth with respect to the wearer's mouth to produce a natural appearance. The fit to the oral tissues, particularly the edentulous gum area of the patient's mouth is critical in the comfort, wearability and aesthetic appearance of the denture and the difficulty in obtaining suitable fit accounts in large part for the cost of providing high quality dentures.
The material which has been developed for prosthetic teeth and gums, i.e., acrylic plastic, has very suitable characteristics in many respects, but the material cannot be directly formed and cured within the patient's mouth due to the difficulty in curing the mass of plastic material which constitutes the complete denture. The use of other materials has been attempted but the bonding of such materials to the prosthetic teeth has not been adequately rigid to prevent the deflection of the teeth and the base material during chewing. This allows gaps to open up during chewing and the denture thus entraps food particles and the denture is thus difficult to keep clean.
It has been proposed and utilized in the past prosthetic dentures in which a hard unitary base structure is provided, with the prosthetic teeth being arranged in a rigid unitary structure extending in a generally U-shape, to which is bonded a soft deflectable liner layer which is formable at relatively low to moderate temperatures compatible with the comfort of the patient during fitting. This liner layer has upward extending flange areas which can be shaped into general conformance with the contacted oral tissues. An intimate fitting is then carried out by lining the deflectable liner layer with a soft, impressionable and hardenable layer coated on the tissue surfaces or disposed on the liner layer after the initial fitting.
A subsequent fitting allows the accurate fitting of the denture to the intimate detail of the patient's mouth, and the denture is then allowed to partially set within the patient's mouth with the curing completed after removal.
This last-mentioned layer also fixes the deflectable liner layer which has previously been partially hardened by freeze spraying or a cold water or ice bath.
This method produces a denture which has adequate rigidity characteristics.
Copending application, Ser. No. 835,143, filed Sept. 21, 1977, solves one problem in this method by taking another approach in the design of the denture: Instead of providing a unitary rigid hard base structure, there is provided a segmented hard base structure, in which individual hard base structure segments are adjustable with respect to each other, allowing a much more accurate alignment of the prosthetic teeth with the mandibular or maxillary gum ridge lines. Alignment of the denture with the gum ridges was a problem with the aforementioned method since the position of the teeth could not be changed during fitting.
Another problem inherent with this approach is that it would be desirable if the incisor teeth and/or cavities were able to be repositioned for purposes of obtaining a more natural appearance and proper bite, or to accommodate existing natural dentition. The use of hard unitary rigid base structure to which the prosthetic teeth are molded precludes any such adjustment at the time of fitting of the denture.
Accordingly, it is an object of the present invention to provide a prosthetic preform in which the position of the anterior teeth may be adjusted during the fitting and in which the anterior teeth thereafter may be molded within a hard rigid base material similar to the base material used to anchor the posterior teeth, to produce a very secure anchoring of these teeth in the prosthetic denture while accommodating such adjustments.
It is a further object of the present invention to provide a method of manufacturing a denture from the fitting impressions taken during the fitting of prosthetic preforms to the wearer's edentulous tissues, either directly by the fitted and cured preform, or from a casting made from flasking the fitted preform in a conventional manner.